Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $115.95   3.259%   $119.7288   $119.73   $119.75   $119.70  
  Purchase #2 $11.27   12.574%   $12.6871   $12.69   $12.70   $12.70  
  Purchase #3 $153.43   9.337%   $167.7558   $167.76   $167.75   $167.80  
  Purchase #4 $246.59   3.870%   $256.133   $256.13   $256.15   $256.10  
  Purchase #5 $121.60   3.499%   $125.8548   $125.85   $125.85   $125.90  
  Purchase #6 $210.48   11.207%   $234.0685   $234.07   $234.05   $234.10  
  Purchase #7 $215.64   11.821%   $241.1308   $241.13   $241.15   $241.10  
  7 purchase totals = $1,074.96       $1,157.3588   $1,157.36   $1,157.40   $1,157.40